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SubjectRe: [PATCH v4 2/2] mm/page_ref: add tracepoint to track down page reference manipulation
On Fri, Mar 04, 2016 at 12:04:39PM -0800, Andrew Morton wrote:
> On Thu, 3 Mar 2016 16:43:49 +0900 Joonsoo Kim <js1304@gmail.com> wrote:
>
> > > Acked-by: Vlastimil Babka <vbabka@suse.cz>
> > >
> > >> +config DEBUG_PAGE_REF
> > >> + bool "Enable tracepoint to track down page reference manipulation"
> > >> + depends on DEBUG_KERNEL
> > >> + depends on TRACEPOINTS
> > >> + ---help---
> > >> + This is the feature to add tracepoint for tracking down page
> > >> reference
> > >> + manipulation. This tracking is useful to diagnosis functional
> > >> failure
> > >> + due to migration failure caused by page reference mismatch. Be
> > >
> > >
> > > OK.
> > >
> > >> + careful to turn on this feature because it could bloat some
> > >> kernel
> > >> + text. In my configuration, it bloats 30 KB. Although kernel text
> > >> will
> > >> + be bloated, there would be no runtime performance overhead if
> > >> + tracepoint isn't enabled thanks to jump label.
> > >
> > >
> > > I would just write something like:
> > >
> > > Enabling this feature adds about 30 KB to the kernel code, but runtime
> > > performance overhead is virtually none until the tracepoints are actually
> > > enabled.
> >
> > Okay, better!
> > Andrew, do you want fixup patch from me or could you simply handle it?
> >
>
> This?

Yep!

Thanks!

>
> --- a/mm/Kconfig.debug~mm-page_ref-add-tracepoint-to-track-down-page-reference-manipulation-fix-3-fix
> +++ a/mm/Kconfig.debug
> @@ -82,10 +82,9 @@ config DEBUG_PAGE_REF
> depends on DEBUG_KERNEL
> depends on TRACEPOINTS
> ---help---
> - This is the feature to add tracepoint for tracking down page reference
> - manipulation. This tracking is useful to diagnosis functional failure
> - due to migration failure caused by page reference mismatch. Be
> - careful to turn on this feature because it could bloat some kernel
> - text. In my configuration, it bloats 30 KB. Although kernel text will
> - be bloated, there would be no runtime performance overhead if
> - tracepoint isn't enabled thanks to jump label.
> + This is a feature to add tracepoint for tracking down page reference
> + manipulation. This tracking is useful to diagnose functional failure
> + due to migration failures caused by page reference mismatches. Be
> + careful when enabling this feature because it adds about 30 KB to the
> + kernel code. However the runtime performance overhead is virtually
> + nil until the tracepoints are actually enabled.
> _
>
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